Method of hot-extruding metals which require a low rate of deformation



Jan. 28, 1969 A. COLLINET Y 3,423,975

METHOD OF HOT-EXTRUDING METALS W H H REQUIRE A LOW 10 RATE OFDEFORMATLON Filed April 18, 1966 PRIOR ART IV I 7 INVENTOR. Alva/Q5COLL/IVE?- A 2 Y a mi M KM 14AM United States Patent 14,174 US. C]. 72425 Claims Int. Cl. B21b 45/02; B21c 23/00 ABSTRACT OF THE DISCLOSURE Amethod for hot-extruding metals and alloys thatrequire a low rate ofdeformation in a fiat-faced die and container by providing the billet tobe extruded with a frustoconical leading portion and inserting prior toextrusion thereof, a solid deformable lubricant in an amount tosubstantially fill the annular space defined by the frustoconicalportion of the billet, the face of the die and the container, and thenextruding said billet.

In the known practice for hot-extruding steels, a flat extrusion die orplate is used, and the front face of the billet has a straight andthereby a planar section which may be joined to its lateral surface by atoroidal surface. The mass of lubricant required for the entireextrusion is then placed as close as possible to the die. This lubricantis generally vitreous and is in a solid deformable form at roomtemperature before the start of the operation. FIG- URE 1 relates tothis known method and in its upper part illustrates an axial section ofa billet I placed in a container 7 with a die 4 before the start of theextrusion and in its lower part, it illustrates the same billet duringthe extrusion.

At the start of the extrusion, the metal flow assumes an outline whichis substantially that of the initial shape of the billet, andprogressive heating of the lubricant 2 assures a continuous supply ofthe lubricant which is viscous and has the appropriate thickness.

This method is satisfactory for extruding carbon steels and low andmedium alloy steels, but it includes the deformation of the metal over avery short distance immediately in front of the bearing land of the die4. Further, this billet must be extruded within a few seconds to preventits cooling whereby these two factors combine to generate very highspeeds or rates of deformation in the mass of the metal. However,certain alloys contains a high proportion of alloy elements which aredescribed as super-refractory, such as super-refractory stainlesssteels, nickel alloys, and molybdenum, tungsten and their alloys, andthese cannot withstand high speeds of deformation without deterioration.Hereinafter, they are referred to as very resistant metals or alloys.

The reduction in cross-section of the metal over a short distanceincludes a pronounced deformation of the glove-finger type of itssuccessive sections, and consequently the formation at the rear end of adeep axial tubular cavity.

To increase the deformation distance, conical dies are employed and thefront face of the billet is shaped so as to plug the entry to the die.FIGURE 2 relates to this known method and in its upper part illustratesan axial section of the billet I placed in position in a container 7before the start of the operation, and in its lower part shows the samebillet during its extrusion. Prior to the extrusion, the mass of thegenerally glass-like lubricant 2 required for the whole extrusion isplaced in position around the lateral surface of the billet, where itimmediately acquires the appropriate temperature and viscosity tolubricate the metal during the extrusion operation.

At the beginning of the extrusion, the flow of metal assumes the preciseshape defined by the entry 3 to the die 4 and it entrains a film oflubricant of appropriate thickness to ensure continuous lubrication ofthe die, even if the extrusion is very fast. This method is satisfactoryfor the extrusion of the very resistant metals and alloys, but it hascertain problems, including difficulty in the production of the dies andhigh costs in their fabrication, for the shape is complex. Also, theapplication of a layer of glass on the billet is an operation whoseresults are sometimes unsatisfactory, and only glasses which possessappropriate viscosity over a wide range of temperatures are used.

This invention avoids the problems encountered in hot extrusion of thevery resistant metals and alloys and provides a deformation distance ofnoteworthy length for the metal. It relates to a method for extrudingthe very resistant metals and alloys in solid or hollow sections andeven in complex sections, and comprises using a fiat die with a billetwhose front portion is a frustoconical body of revolution. The methodincludes filling the annular space formed between the surfaces of thedie and the billet with a generally gass-like lubricant, having a soliddeformable form such as agglomerated glass powder, fibreglass andmulti-cellular glass.

The front face of the billet is formed into a frustoconical body ofrevolution whose small base 5 substantially fits into the section of theproduct to be produced, and whose large base 6 and small base circlesare rounded off toroidally, for example, with a radius of 20 mm. Theangle at the base of the frustoconical body is preferably between 30 and60.

FIGURE 3 relates to the method of the invention and in its upper partillustrates an axial section of the billet 1 placed in position in acontainer 7 prior to the start of the extrusion, and in its lower partshows the same billet during the extrusion. To perform the extrusion'andbefore insertion of the =billet into the container 7, a volume ofvitreous lubricant is placed in position in the container against thedie. This volume exceeds slightly, after compression, the volume ofmetal removed from the cylindrical billet to form its front extremity.It is advantageous to make this volume of lubricant of several rings ofagglomerated glass powder 2a having the same diameter as the billet andpierced in such manner as to leave the aperture of the die largelyunobstructed.

When the billet is compressed before the extrusion, the front of thebillet advances its conical portion into the mass of the glass andcompresses it into the angle formed in the front of the container withthe die. By flowing towards the different parts of the die aperture, themetal creates the most suitable junction surfaces in the mass of glassbetween its conical form and the die aperture. Over a substantial partof its surface, the flat die is thus separated from the billet by asubstantial thickness of insulating lubricant, which limits its heatingand thereby enhances its life.

To avoid losses of the very resistant metal or alloy from machining theconical front portion, the method also comprises retaining a flat frontsurface of the billet, which may or may not be joined to the lateralsurface by a toroidal surface. To this front face is afiixed, connectedor placed a frustoconical element of carbon steel delimited at the frontas specified herein, and delimited at the rear as required for the frontface of the billet. The metal flow is the same, and some of the lossesof the very resistant metal or alloy which is frequently expensive isavoided.

EXAMPLE In production of 38 x 38 x 10 mm., from a nickel alloycontaining 16% Mo, 15.5% Cr, 5% Fe, 4% W, 2.5% Co, 1% Mn, 1% Si, 0.08%C, the balance being Ni, the cylindrical billets were employed and theyhad an overall length of 270 mm., a diameter of 120 mm., Whose frontextremity had simply been turned to frustoconical shape with a baseangle of 45, with a small base of a diameter of 30 mm., and with aradius of 15 mm. along each base circle.

The extrusion press had a force of 1,500 tons and was equipped with a126 mm. diameter container which terminated in a flat die and adie-holder. Before each extrusion, 3 pierced discs of agglomerated glasspowder 122 mm. in diameter and 20 mm. in thickness were placed inappropriate direction against the die. The first disc had an L-shapedbore in dimensions of 60x60x30 mm. The second disc had a circular bore70 mm. in diameter and the third disc had a circular bore 90 mm. indiameter.

The extrusion was controlled so as to leave a plug of a thickness of mm.This rendered it possible to obtain sections free of cracks andimperfections, and free of any tubular cavity at their rear ends.

While I have shown and described preferred embodiments of my invention,it may be otherwise embodied within the scope of the appended claims.

I claim:

1. A method of hot-extruding metals and alloys that require a low rateof deformation in a container and flatfaced die, comprising:

(A) forming a substantially frustoconical leading portion on a billet tobe extruded;

(B) placing adjacent the flat face of the die a lubricant in a soliddeformable state when cold and in an amount to substantially fill thearea defined by the container, the die face and the frustoconicalportion when the leading end of the billet is adjacent the die;

(C) inserting the billet heated to extrusion temperature into saidcontainer; and,

(D) extruding the billet through the die.

2. The method of claim 1 wherein said billet is so formed that thefrustoconical surface of said leading portion is disposed at an angle ofsubstantially between and relative to the central longitudinal axis ofsaid billet.

3. The method of claim 1 wherein said lubricant comprises discs ofagglomerated glass powder pierced centrally thereof to substantiallysurround the aperture of said die.

4. The method of claim 1 wherein said billet is so formed that thefrustoconical surface of said leading portion is disposed at an angle ofsubstantially between 30 and 60 relative to the central longitudinalaxis of said billet and wherein said lubricant comprise discs ofagglomerated glass powder pierced centrally thereof to substantiallysurround the aperture of said die.

5. The method of claim 1 wherein said amount of said lubricant is atleast that volume of metal removed from said billet in formation of saidfrustoconical portion.

References Cited UNITED STATES PATENTS 2,806,596 9/1957 Dodds et al.72-42 2,946,437 7/1960 Edgecombe 72-253 3,059,769 10/1962 Frost 72-423,072,251 1/1963 Sauve 72-42 3,255,621 6/1966 Ohsol 72-42 CHARLES W.LANHAM, Primary Examiner.

E. M. COMBS, Assistant Examiner.

US. Cl. X.R. 72 2s3, 41

